1. Field of the Invention
The present invention relates to a detection method for detecting knocking in an internal combustion engine and an ignition timing control method utilizing said detection method.
2. Description of Prior Art
As is well known, knocking is a phenomenon resulting from a self-ignition of unburned gas remaining in the extremity region of the combustion chamber, and causing vibration in the gas inside the combustion chamber, consequently propagating thus generated vibration to the engine body itself.
Since this knocking gives rise to a loss of energy in the engine output, exerts mechanical shock on the components of the engine as well as lowers the fuel consumption and the like, it is desired to be avoided as much as possible. For this purpose, it is indispensable for a precise detection of the occurrence of a knocking to be ensured to be made.
Reflecting such requirements, there has been proposed a prior art as set forth in the Japanese Patent Laid-open No. 58-45520/1983 wherein the occurrence of knocking is detected by going through the steps of separating a single resonance frequency component in the range of 5 to 12 kHz in the output signals from the vibration detection sensor with a band pass filter, integrating the output thereof, and determining whether an integrated value is greater than the background level thereof.
However, such knocking detection method based on the single resonance frequency component involves such problems that the background level thereof becomes larger at a faster the engine speed thereby preventing a precise detection of knocking, and that the knocking resonance frequencies tend to change with varying engine data, thereby impeding precise detection of knocking.